When preparing his gnudi, Francesco Buitoni of Mercato Osteria & Enoteca uses goat cheese and ricotta impastata, a high quality ricotta that's been drained to achieve a buttery consistency. If you can't find some (some Italian grocers may carry it), wrap premium ricotta in cheesecloth and let it drain in the refrigerator. Cavolo nero is often sold as Tuscan kale, Lacinato, or dinosaur kale.
Get the recipe here.